Directional asymmetries in the length‐response profiles of cells in the feline dorsal lateral geniculate nucleus.

Abstract

1. The visual cortex provides a major synaptic input to the dorsal lateral geniculate nucleus (dLGN). Cortical layer VI cells giving rise to this projection are strongly influenced by stimulus orientation, length and direction of motion. In the dLGN, a significant component of the strong length tuning exhibited by most cells follows from the corticofugal influence. We have now checked whether there are directional biases in geniculate cell responses, and whether such biases are influenced by stimulus length. 2. The responses of A‐laminae dLGN cells were assessed by single‐unit extracellular recording. Length preference was examined by plotting multihistogram length‐tuning curves to moving bars of light of various length. 3. Over half of the cells tested (100/183) exhibited directional bias and in many cases, this bias was highly dependent on bar length, resulting in radically different length response profiles for the two directions of motion. These asymmetries are similar to those documented for cortical hypercomplex cells, but do not equate to any known facet of the centre‐surround organization of dLGN cell receptive fields. 4. We suspected the directional biases followed from the influence of the corticofugal projection. To test this, we recorded from preparations where areas 17 and 18 of the visual cortex had been removed. Surprisingly, a similar proportion of cells exhibited directional biases after removal of the corticofugal input, suggesting that the biases are generated subcortically. 5. The widespread presence of systematic biases in the response profiles of dLGN cells further underlines the possibility that geniculate mechanisms may make a far greater contribution to visual processing than hitherto suspected.

Multitasking of Attention and Memory Functions in the Primate Prefrontal Cortex

“…Neurons in visual areas can switch tuning preferences depending on the eye used or stimulus length, shape, speed, depth, or location in the visual field (Zeki, 1974;Poggio and Fischer, 1977;Poggio and Talbot, 1981;Jones and Sillito, 1994;Okamoto et al, 1999;Tanaka et al, 1999Tanaka et al, , 2002Anzai et al, 2007) (cf. Maunsell andVan Essen, 1983).…”

Evidence for a contribution of lateral inhibition to orientation tuning and direction selectivity in cat visual cortex: reversible inactivation of functionally characterized sites combined with neuroanatomical tracing techniques

“…Because in most cases both the recording and inactivation sites were located in layers III–IV, which contain a high proportion of cells receiving a monosynaptic thalamic input (Harvey 1980; Ferster & Lindström 1983; Martin & Whitteridge 1984), many of the present effects may have reflected the loss of a rapid (disynaptic) inhibitory input to recurrently connected, monosynaptically excited cells. An orientation/direction preference could be conferred upon first‐order inhibitory (and excitatory) neurons via an oriented convergence of thalamocortical afferents (Hubel & Wiesel 1962) or an orientation/direction biased input from thalamic relay cells (Vidyasagar & Urbas 1982; Jones & Sillito 1994; Thompson et al . 1994a,b).…”

“…Because in most cases both the recording and inactivation sites were located in layers III-IV, which contain a high proportion of cells receiving a monosynaptic thalamic input (Harvey, 1980;Ferster & Lindström, 1983;Martin & Whitteridge, 1984), many of the present effects may have reflected the loss of a rapid (disynaptic) inhibitory input to recurrently connected, monosynaptically excited cells. An orientation/ direction preference could be conferred upon first-order inhibitory (and excitatory) neurons via an oriented convergence of thalamocortical afferents (Hubel & Wiesel, 1962) or an orientation/direction biased input from thalamic relay cells (Vidyasagar & Urbas, 1982;Jones & Sillito, 1994;Thompson et al, 1994a,b). Although Ferster et al (1996) have recently claimed that the thalamic input is sufficient to generate orientation tuning in first-order simple cells in area 17, their results are actually not inconsistent with a contribution of intracortical circuitry to cortical orientation selectivity (Sompolinsky & Shapley, 1997; and see discussion in Crook et al, 1997).…”

Refractory density model of cortical direction selectivity: Lagged-nonlagged, transient-sustained, and On-Off thalamic neuron-based mechanisms and intracortical amplification

“…One of the questions is whether DS is inherited from the directionally selective subcortical neurons (mainly geniculate cells) or is reconstructed in the cortex de novo. DS of geniculate cells is well-documented for lagomorphs and rodents [ 10 ], but data on carnivores and primates point to some directional bias in geniculate cells rather than a prominent DS [ 11 , 12 ]. Recently, Lien and Scanziani [ 13 ] used an optogenetic approach to show that even in mice, the cortical DS emerges de novo at the convergence of thalamic synapses on the same cortical neuron, whereas at the geniculate level, DS is negligible.…”